Assessment Of Changes Following Different Retraction Techniques With Different Anchorages In Adult Women With Premolars Extraction

After the first stage of the Straight Arch wire Techniques,the crowded tooth,the vertical and lateral problems were basically solved,hen to close the space of tooth extraction is the next target.We often use two-step retraction and en-mass retraction to close the space.Closing loop and sliding machine are the optimal ways to accomplish this stage target.En-mass retraction is a method that retracted all the anterior teeth,two-step retraction is that retracted the canine teeth first,then the incisor teeth.There still have been controversies about what methods is better in achieving maximum anchorage.The anchorage teeth must be moved in the retraction of anterior teeth.The best way to protect anchorage is to control the teeth to move along a certain direction and distance as we designed,also the teeth used as anchor in the treatment not moving or just a little.The key of the successful treatment is control anchorage in a proper way.We often use Nance arch or transpalatal arch(TPA)to enhance the resistance in clinical treatment.According the research,the combination of Nance arch and transpalatal arch can reinforce the resistance in three-dimensional space.Our study was to compare the difference of one-step and two-step retraction,closing loop technique and sliding technique,Nance arch and transpalatal arch in the resistance control and provide certain reference basis for clinical selection of resistance and space close approach.ObjectiveTo compare the differences of first maxillary molar and anterior teeth position change by using one-step and two-step retraction,closing loop technique and sliding technique,Nance arch and transpalatal arch in the adult female extraction patients with Class I malocclusion.Material and methods 1.MaterialThis study is a retrospective study,The subjects in this study included 240 adult female patients with Class I malocclusion and four first premolars extraction,treated in the Department of Orthodontics,The Fourth Military Medical University from 2013 to 2015.Because of the completely of data,the initial sample only consisted of 120 adult female patients which were divided according to different space closing skills and the resistance types.2.Methods1)There were 19 representative measurement indexes,including 10 teeth related indicators,9 skeletal related indicators.All statistical analyses were based on comparison of first maxillary molar and anterior teeth position changes measured on the pre-(T1)and post-treatment(T2)lateral cephalometrics.2)All statistical analyses were performed with SPSS software(version 19.0).All the data fitted normal distribution by single sample K-S test.Treatment changes between groups were compared with an independent-samples t test.And the levels of statistical significance were ? =0.05.Results 1.Variation of upper molarsThere were no significant differences in the degree of anchorage loss of the maxillary posterior teeth between one-step and two-step retraction.The maxillary posterior teeth is moved mesially about 3mm in the maximum posterior anchorage and 2mm in maximum anchorage.There were no significant differences in the degree of anchorage loss of the maxillary posterior teeth between one-step and two-step retraction.(p>0.05).There were no significant differences in the degree of the inclination of maxillary posterior teeth between one-step and two-step retraction.The inclination of maxillary posterior teeth is litter than maximum posterior anchorage.There were no significant differences in vertical control in these groups.No significant differences between the transpalatal arch and Nance arch groups in terms of prevention of mesial drift,vertical displacement and distal tipping(p>0.05).No significant differences between closing loop technique and sliding technique in terms of prevention of mesial drift,vertical displacement and mesial tipping(p>0.05).Bodily and mesial movements of the upper molars in the sliding technique group is less than closing loop group,and the vertical displacement of the upper molars is more too.2.Comparison of anterior teeth retractionThere were no significant differences in the degree of anterior teeth retraction between one-step and two-step retraction.Both groups can better cantor the anterior teeth no matter what resistance they have.The retraction of incisal edge and apex is about 6:1.No significant differences between the transpalatal arch and Nance arch groups in terms of prevention of vertical displacement(p>0.05).However,there was a statistically significant difference in the amount of anterior teeth retraction between the arch types(p<0.05).TPA(-14.74 ±5.82°)Nance arch(-9.31±3.97°).There were no significant differences in the degree of anterior teeth retraction between closing loop technique and sliding technique.The retraction of incisal edge and apex is about 6:1 in the group of closing loop,and better correct the position of anterior teeth.Conclusion1.From the view of the sagittal direction.No significant differences in each groups whatever closing techniques they use in terms of prevention of mesial drift,and the molars anchorage could be better protected in these groups.2.From the view of the vertical direction.There was no difference in the one-step and two-step retraction,closing loop technique and sliding technique,Nance arch and transpalatal arch in the resistance control,better vertical control can be provided in each group.3.From the view of the molar tipping.No significant differences in each groups whatever closing techniques they use in terms of prevention of mesial tipping.